The invention relates generally to hydraulic valves, and, more particularly, to hydraulic valves in which the position of a movable spool or poppet can be detected.
Hydraulic valves are used to regulate the flow and pressure of hydraulic fluid in a variety of types of devices, ranging from construction equipment like bulldozers and power shovels to jet aircraft. Many hydraulic valves use a spool or poppet that changes position within the valve to control the amount of hydraulic fluid passing through the valve per unit of time. One challenge in using such valves is determining the current position of the spool or poppet at any given time. Since the spool or poppet is typically located inside the valve and is not visible, the information can be difficult to obtain.
In accordance with the foregoing, the invention is generally directed to a hydraulic valve with a position sensor. According to various embodiment of the invention, the valve has a cage with a set of radial holes, a spool assembly slideable within the cage, and a sensor, which may be a Hall effect sensor, that provides an electrical signal based on the position of the spool assembly. In more specific embodiments, the spool assembly comprises one or more of the following: a spool, a pin having an enlarged portion and mechanically coupled to the spool and a biasing means, which may be a spring, having a first and a second end, the first end being in contact with the pin and the second end being in contact with the spool.
In other embodiments of the invention, the spool assembly comprises a generally cylindrical guide aligned with the spool and in contact with an end surface of the spool, the guide having a longitudinal hole and at least a portion of the pin being disposed within the longitudinal hole. The spool assembly may also comprise a biasing means disposed within the longitudinal hole, a first end of the biasing means being in contact with the portion of the pin that is disposed within the longitudinal hole and a second end of the biasing means extending out from the longitudinal hole and in contact with the spool. In more specific embodiments, the longitudinal hole of the guide may have a first and a second section, the first section being smaller in diameter than the second section, a circular step of the guide being defined between the first and second sections, wherein, during operation of the valve, the circular step limits the movement of the enlarged portion of the pin to prevent the pin from exiting the longitudinal hole of the guide.
In yet other embodiments of the invention, the valve comprises a spool having a longitudinal blind hold at one end, a portion of a guide being disposed within the longitudinal blind hole, wherein the guide has a collar that is disposed outside of the longitudinal blind hole and is in contact with an end of the spool. The valve may further comprise a plug disposed at an end of the valve, a sensor held stationary by the plug, and a spring annularly disposed around the guide, wherein a first end of the spring abuts the plug and a second end of the spring abuts the annular collar of the guide, wherein the spring pushes the guide and the spool away from the plug.
According to still other embodiments of the invention, a safety system for a hydraulic device, comprises a hydraulic valve that, by itself, comprises: a cage having a set of radial holes for allowing the passage of fluid; a spool slideable within the cage to allow or block the flow of fluid through the set of radial holes, the spool having at least a first position and a second position; a pin coupled to the spool; and a sensor disposed adjacent to the pin, wherein when the spool moves from the first position to the second position, the pin moves relative to the sensor, thereby causing a change in a magnetic field near the sensor, wherein the sensor reacts to the change by generating an electrical signal. The safety system may further comprise a safety circuit electrically connected to the sensor, wherein the safety circuit allows or prevents a user from activating the hydraulic device based on the electrical signal generated by the sensor.